Ran Xu

Hunan University, Ch’ang-sha-shih, Hunan, China

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Publications (2)8.62 Total impact

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    ABSTRACT: In the present work, microwave heating initiated precipitation polymerization was developed to prepare podophyllotoxin (PPT) molecularly imprinted polymers (MIPs), resulting in much shorter polymerization time and better particle morphology. Prior to the polymerization, ultraviolet and FTIR spectroscopy were used to study the interactions between PPT and the functional monomers. The synthesized parameters were respectively optimized and the optimal conditions for the efficient adsorption property were template: PPT, 1 mmol; functional monomer: acrylamide, 6 mmol; bi-crosslinker: ethylene glycol dimethacrylate, 20 mmol and divinylbenzene, 20 mmol; porogen: acetonitrile, 40 mL; initiator: azobisisobutyronitrile, 0.01mol L⁻¹; polymerization temperature: 60°C. FTIR spectroscopy, SEM and thermal analysis were used to characterize the MIPs. The results of the equilibrium rebinding experiments and the competitive adsorption experiments showed that these imprinted polymers exhibited good adsorption ability for the PPT. Scatchard analysis illustrated that two and one types of binding sites were generated in the MIPs and non-imprinted polymers (NIPs), respectively. Using the prepared MIPs as the solid phase extraction (SPE) sorbent, PPT was extracted selectively and efficiently from Dysosma versipellis, Sinopodophyllum hexandrum and Diphylleia sinensis. The regression equation was y=5.873×10⁶x+17075.659 with the correlation coefficient of 0.9994 in the concentration range of 0.005-0.4 mg mL⁻¹. After washing and eluting the SPE column with methanol and MeOH/acetic acid solution (v/v, 9:1), the limits of detection were 0.12-0.18 μg mL⁻¹ and their recoveries were in the range of 89.5-91.1% with all RSDs lower than 3.7.
    No preview · Article · Jun 2011 · Analytica chimica acta
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    ABSTRACT: A micelle-mediated extraction technique, i.e. ionic liquid-based microwave-assisted extraction (ILs-MAE) technique has been developed for the effective extraction of podophyllotoxin from three Chinese medicinal plants. Several operating parameters were successively optimized by single-factor and L(9) (3(4)) orthogonal array experiments. 1-Butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF(4)]), 1-decyl-3-methylimidazolium tetrafluoroborate ([demim][BF(4)]) and 1-allyl-3-methylimidazolium tetrafluoroborate ([amim][BF(4)]) were selected as the optimal surfactants for Dysosma versipellis, Sinopodophyllum hexandrum and Diphylleia sinensis, respectively. Compared with other extraction techniques, such as ionic liquids-based maceration extraction (ILs-ME), heat extraction (ILs-HE) and ultrasound-assisted extraction (ILs-UAE), the ILs-MAE technique not only took a shorter time but also afforded a higher extraction rate of podophyllotoxin from the herbs. Reversed phase high performance liquid chromatography was employed for the analysis of podophyllotoxin. The results showed that the linearity for analyzing podophyllotoxin in all three herbs was in the concentration range of 0.005-0.4 mg mL(-1) with the correlation coefficient between 0.9993 and 0.9996. LODs were 2.05-2.58 μg mL(-1) and RSDs of inter-day stability were less than 5.8%. Repeatability and intermediate precision were separately lower than 3.3% and 6.3%. The recoveries for podophyllotoxin extracted with the ILs-MAE technique were in the range of 97.1-102% and all RSDs were lower than 3.0%. Furthermore, the mechanism of ILs-MAE was preliminarily studied by means of kinetic mechanism, surface structures and chemical compositions of samples before and after different extraction techniques. On the basis of the destruction of herb surface microstructures and high solubility of ILs, the ILs-MAE technique eventually got the maximum yield value.
    No preview · Article · Apr 2011 · The Analyst